Chip Caltech steers light in 74 femtoseconds

The device is a metasurface made of amorphous silicon. It has nanopillars on it. They force light to circulate inside the material a bit longer, thereby amplifying the weak optical Kerr effect. A short “pump” pulse slightly changes how electrons move along their orbits. The refractive index jumps. Because of this, a second, probe beam is deflected—by up to 13 degrees in experiments.

74 femtoseconds here is not a material limit, but the duration of the pulse itself. A shorter laser pulse could, in theory, produce even faster steering. The electrons are not driven into long-lived excited states, so the scheme doesn’t have to wait for the semiconductor to “cool down.”

Why anyone would need this beyond a paper. Photonic chips, communications, sensors, computing with light—anywhere you don’t want to convert a signal into current and back. For now, the angle is modest, and the Kerr enhancement relies on the geometry of the pillars. It’s a long way from a rack in a data center. But it introduces a steering wheel that clicks faster than electronics can blink.

Sources:

1. Caltech. "Caltech’s tiny new chip can steer light in 74 quadrillionths of a second." ScienceDaily (18 September 2026).
2. Hail C.U., Michaeli L., Atwater H.A. "Ultrafast, reconfigurable all-optical beam steering and spatial light modulation." Nature Nanotechnology (2026). DOI: 10.1038/s41565-026-02199-w.

Illustration: Claudio Hail